Progress vs. Variation -- Part IV
Feb. 18th, 2004 11:00 am![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
prof_pangaeaAn argument against "progress" and instead for INCREASING VARIATION in evolution, from Full House, by Stephen Jay Gould
4. The myopia of characterising a full distribution by an extreme item at one tail.
The only conceivable argument for general progress must postulate that an expanding right tail [of the bell curve] demonstrates a predictable upward thrust of the whole. But such a claim only embodies the silly spectacle of a small tail wagging a large dog. (We have generall failed to grasp the evident absurdity because we have not visualised the dog properly; rather, in a move that recalls the Chesire cat of Wonderland, identified only by its smile, we have characterised the whole entire dog by its tail alone).
A claim for general progress based on the right tail alone is absurd for two primary reasons: First, the tail is small and occupied by only a tiny percentage of species (more than 80 percent of multicellular animal species are arthropods, and we generally regards all members of this phylum as primitive and nonprogessive). Second, the occupants of the extreme right edge through time do not form an evolutionary sequence, but rather a motley series of disparate forms that have tumbled into this position, one after another. Such a sequence through time might read: bacterium, eukaryotic cell, marine alga, jellyfish, trilobite, nautiloid, placoderm fish, dinosaur, sabertoothed cat, and homo sapiens. Beyond the first two transitions, not a single form in the sequence can possibly be a direct ancestor of the next in line.
4. The myopia of characterising a full distribution by an extreme item at one tail.
The only conceivable argument for general progress must postulate that an expanding right tail [of the bell curve] demonstrates a predictable upward thrust of the whole. But such a claim only embodies the silly spectacle of a small tail wagging a large dog. (We have generall failed to grasp the evident absurdity because we have not visualised the dog properly; rather, in a move that recalls the Chesire cat of Wonderland, identified only by its smile, we have characterised the whole entire dog by its tail alone).
A claim for general progress based on the right tail alone is absurd for two primary reasons: First, the tail is small and occupied by only a tiny percentage of species (more than 80 percent of multicellular animal species are arthropods, and we generally regards all members of this phylum as primitive and nonprogessive). Second, the occupants of the extreme right edge through time do not form an evolutionary sequence, but rather a motley series of disparate forms that have tumbled into this position, one after another. Such a sequence through time might read: bacterium, eukaryotic cell, marine alga, jellyfish, trilobite, nautiloid, placoderm fish, dinosaur, sabertoothed cat, and homo sapiens. Beyond the first two transitions, not a single form in the sequence can possibly be a direct ancestor of the next in line.
